Preconditioned illuminator system and method

ABSTRACT

Embodiments of endo-illuminators and related methods are disclosed. One embodiment of an illuminator can comprise a cannula defining a passage, an optical element disposed at an end of the cannula, and an optical fiber running through the passage with the distal end of the optical fiber in contact with the optical element. The optical fiber includes at least a heat preconditioned distal portion that terminates in the distal end that is in contact with the optical element.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of prior application Ser.No. 12/540,755, filed Aug. 13, 2009, which claims the benefit of U.S.Provisional Application No. 61/088,484, filed Aug. 13, 2008.

TECHNICAL FIELD OF THE INVENTION

Systems and methods disclosed herein relate generally to surgicalinstrumentation. In particular, the systems and methods relate tosurgical instruments for illuminating an area during eye surgery. Evenmore particularly, the systems and methods relate to illuminators forillumination of a surgical field that are preconditioned to relievestress.

BACKGROUND OF THE INVENTION

In ophthalmic surgery, and in particular in vitro-retinal surgery, it isdesirable to use a wide-angle surgical microscope system to view aslarge a portion of the retina as possible. Wide-angle objective lensesfor such microscopic systems exist, but they require a widerillumination field than that provided by the cone of illumination of atypical fiber-optic probe. As a result, various technologies have beendeveloped to increase the beam spreading of the relatively incoherentlight provided by a fiber-optic illuminator. These known wide-angleilluminators can thus illuminate a larger portion of the retina asrequired by current wide-angle surgical microscope systems.

Current wide-angle illuminators can experience run-away heating thatdegrades the performance of the illuminator. Run-away heating occurswhen the cannula of an illuminator absorbs light from the optical fiberrunning through the illuminator and, consequently, increases intemperature. As the cannula heats, the optical fiber may begin todeform, causing even more light to be incident on the cannula,increasing the temperature of the cannula further and, hence, increasingthe deformation in the optical fiber. This cycle can lead tocatastrophic failure of the illuminator.

SUMMARY

The various embodiments of the method and system of the presentinvention provide for an illuminator that is resistant to run-away heatdeformation. In general, the optical fiber of the illuminator undergoesheat preconditioning at its distal portion to relieve axial stress atthe distal portion prior to or in lieu of the distal portion being fixedin place relative to other components of the illuminator. Suchpreconditioned illuminators can be used for longer periods of time usingmore intense light than traditional illuminators.

According to one embodiment, an illuminator can comprise a cannuladefining a passage, an optical element disposed at a distal end of thecannula, and an optical fiber running through the passage with thedistal end of the optical fiber in contact with the optical element. Theoptical fiber includes at least a heat preconditioned distal portionthat terminates in the distal end that is in contact with the opticalelement.

One embodiment of preconditioning an illuminator can comprise insertingan optical fiber through a proximal portion of a cannula/optical elementassembly until the distal end of the optical fiber contacts the opticalelement, heating a distal portion of the optical fiber to between asoftening temperature and a melting temperature for a period of time tocause the distal portion to axially shrink and moving the opticalelement so that the optical element is in contact with the distal end ofthe optical fiber when the distal portion of the optical fiber hasaxially shrunk. Moving the optical element so that the optical elementis in contact with the distal end of the optical fiber when the distalportion of the optical fiber has axially shrunk can comprise applying aforce to the cannula/optical element assembly to maintain the opticalelement in continuous contact with the distal end of the optical fiberwhile the optical fiber axially shrinks. In a vertical arrangement, thiscan be done through the force of gravity.

Yet another embodiment of an illuminator method comprises inserting anoptical fiber through a proximal portion of a cannula until the distalend of the optical fiber contacts a lens, vertically aligning thecannula with an opening defined by a heating member, lowering theheating member until the cannula is inserted a desired insertion depthin the opening, heating a distal portion of the optical fiber to betweena softening temperature and a melting temperature for a period of timeto cause the distal portion to axially shrink and allowing the cannulato move so that the lens remains in contact with the distal end of theoptical as the distal portion axially shrinks.

BRIEF DESCRIPTION OF THE FIGURES

A more complete understanding of the various embodiments and theadvantages thereof may be acquired by referring to the followingdescription, taken in conjunction with the accompanying drawings inwhich like reference numbers indicate like features and wherein:

FIG. 1 is a simplified diagram of a surgical system;

FIG. 2 is a diagrammatic representation of a portion of an illuminator;

FIG. 3 is a graph showing data for run-away thermal deformation;

FIG. 4A is a diagrammatic representation of one embodiment of a systemfor preconditioning an illuminator;

FIG. 4B is a diagrammatic representation of one embodiment of anarrangement during preconditioning an illuminator;

FIG. 5 is a diagrammatic representation of another embodiment of asystem for preconditioning an illuminator;

FIG. 6 is a graph illustrating resistance to run-away thermaldeformation due to preconditioning;

FIG. 7 is a graph illustrating optical performance for a preconditionedversus non-preconditioned illuminator; and

FIG. 8 is another graph illustrating optical performance for apreconditioned versus non-preconditioned illuminator.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention are illustrated in theFIGURES, like numerals being used to refer to like and correspondingparts of the various drawings.

FIG. 1 is a simplified diagram of a surgical system 2 comprising ahandpiece 10 for delivering a beam of light, which can be incoherentlight, from a light source 12 through cable 14 to the distal end of astem (cannula) 16. Handpiece 10 can be any surgical handpiece as knownin the art, such as the Revolution-DSP™ handpiece sold by AlconLaboratories, Inc. of Fort Worth, Tex. Light source 10 can be a xenonlight source, a halogen light source, or any other light source capableof delivering relatively incoherent light which can be transmittedthrough a fiber optic cable. By way of example, but not limitation,light source 10 can be an Accurus High Brightness Illuminator or aConstellation Illuminator, both manufactured and sold by AlconLaboratories, Inc. Cable 14 can comprise a proximal optical fiber 13 ofany gauge fiber optic cable as known in the art, but proximal opticalfiber 13 is preferably a 20 or 25 gauge compatible fiber. Cannula 16 canbe a small gauge cannula, preferably on the order of 19, 20, 23 or 25gauge, as known to those having skill in the art. Stem 16 can bestainless steel or a suitable biocompatible polymer (e.g., PEEK,polyimide, etc.) as known to those having skill in the art. Cannullal 6is configured to house a distal optical fiber 20, as is more clearlyillustrated in FIG. 2. Coupling system 32 can comprise an optical fiberconnector at the proximal end of optical cable 14 to optically couplelight source 12 to proximal optical fiber 13 within optical cable 14.

The proximal optical fiber 13, distal optical fiber 20 and/or stem 16can be operably coupled to the handpiece 10, for example, via anadjusting mechanism. The adjusting mechanism can comprise, for example,a simple push/pull mechanism as known to those having skill in the art.Light source 12 can be operably coupled to handpiece 10 (i.e., opticallycoupled to proximal optical fiber 13 within optical cable 14) using, forexample, standard SMA (Scale Manufacturers Association) optical fiberconnectors at the proximal end of fiber optic cable 14. This allows forthe efficient transmission of light from the light source 12 to asurgical site through proximal optical fiber 13, passing withinhandpiece 10, through tapered section 26 (whether separate or integralto distal optical fiber 20) and optical fiber 20 to emanate from thedistal end of distal optical fiber 20 and stem 16. Light source 12 maycomprise filters, as known to those having skill in the art, to reducethe damaging thermal effects of absorbed infrared radiation originatingat the light source. The light source 12 filter(s) can be used toselectively illuminate a surgical field with different colors of light,such as, for example, to excite a surgical dye.

FIG. 2 is a diagrammatic representation of a portion of one embodimentof an endo-illuminator of the present invention including a cannula 16,a distal optical fiber 20 and a proximal optical fiber 13. Distaloptical fiber 20 can be optically coupled to proximal optical fiber 13at coupling 30, which can, in turn, be optically coupled to light source12 (see FIG. 1) to receive light from the light source 12. Proximaloptical fiber 13 can be a larger diameter, small NA (e.g., 0.5 NA)optical fiber, such as a 20 gauge compatible optical fiber. Distaloptical fiber 20 can be a high numerical aperture (“NA”), smallerdiameter (e.g., 25 gauge compatible) optical fiber or light pipe (e.g.,cylindrical light pipe) located downstream of the proximal opticalfiber. An optical element 26 is in contact with the distal end of distaloptical fiber 20. One or more of proximal optical fiber 13 or distaloptical fiber 20 may include a protective sheath made out of a suitablematerial, such as PVC or other material.

Fiber(s) 20 is terminated by optically coupling to optical element 26.Optical element 26 can be an optical grade sapphire diffuser having ahemispherical or slightly larger than hemispherical shape. Opticalelement 26 can comprise a polished flat surface 28 at the distal end ofstem 16 (i.e., facing out towards a surgical field) and a hemisphericalsurface 29 facing the distal end of fiber 20. Optical element 26 issized for housing within stem 16 (e.g., a 19 to 30 gauge cannula). Forexample, optical element 26 can have a diameter of about 0.75 mm toabout 0.4 mm. The flat surface 28 of optical element 26 can beco-incident with the open aperture at the distal end of stem 16.

The embodiment of the high throughput endo-illuminator of this inventionillustrated in FIG. 2 comprises a low-NA, larger diameter proximaloptical fiber 13 optically coupled to a tapered, high-NA, smallerdiameter distal optical fiber 20. The proximal optical fiber 13 can be a0.50 NA plastic fiber (e.g., to match the NA of the light source 12),having a polymethyl methacrylate (PMMA) core and a 0.030″ (750 micron)core diameter, or another such comparable fiber as known to those havingskill in the art. For example, such a fiber is compatible with thedimensions of the focused light spot from a 20 gauge light source 12,such as the ACCURUS® illuminator manufactured by Alcon Laboratories,Inc. of Fort Worth, Tex. As one example, suitable fibers for theproximal optical fiber 13 of the embodiments of this invention areproduced by Mitsubishi (Super-Eska fiber), which can be purchasedthrough Industrial Fiber Optics, and Toray, which can be purchasedthrough Moritex Corporation.

Suitable fibers for the distal optical fiber 20 (downstream fiber) arePolymicro's High OH (FSU), 0.66 NA, silica core/Teflon AF clad opticalfiber, having a core diameter that can be custom-made to requiredspecifications and Toray's PJU-FB500 0.63 NA fiber (486 micron corediameter). Proximal optical fiber 13 and distal optical fiber 20 can beoptically coupled together using any suitable mechanism known to thoseskilled in the art.

In the embodiment of FIG. 2, the endo-illuminator comprises a proximaloptical fiber 13 coupled to a distal optical fiber 20 at a coupling 30.Various methods of coupling optical fibers are described in U.S. patentapplication Ser. No. 11/354,615 entitled “High ThroughputEndo-Illuminator Probe”, filed Feb. 15, 2006, by Alcon Research, Ltd.,which is hereby fully incorporated by reference herein.

Cannula/optical element assembly 32 can be formed by selecting a cannula16 of a desired diameter, such as a 23 gauge or 25 gauge cannula,selecting an optical element material that is slightly larger than theinner diameter cannula 16 and press fitting the optical element materialinto the cannula. For example, a sapphire ball can be selected and pressfit into the distal end of cannula 16. The optical element material canthen be ground to a desired shape. In one embodiment, for example, thesapphire ball (and potentially the end of the cannula) can be groundaway until the remaining optical element 26 is slightly larger thanhemispherical.

According to one method of assembly, the distal optical fiber 20 is slidinto the proximal end of cannula 16 until the distal end of distaloptical fiber 20 contacts the optical element 26. If the cannula 16 wereto be bonded at this point to optical fiber 20 without preconditioningoptical fiber 20, the resulting device is more susceptible to experiencerunaway heating and catastrophic failure during use. This resultsbecause plastic optical fiber is created through a drawing process thatstretches the fiber axially before it hardens, causing potential energyto be stored in the fiber. When the fiber is heated and the softeningpoint reached (around 105©), the potential energy is released by axialshrinking and lateral swelling of the fiber.

When a high-luminance xenon light is coupled to the fiber, a significantamount of luminous flux passes through the distal end of the probethrough optical element 26 to illuminate the retina. However, fromdistal fiber 20, some amount may be absorbed by cannula 16, causing thedistal end of cannula 16 and consequently the distal portion of distalfiber 20 to increase in temperature. If the temperature becomes highenough, the distal portion of distal fiber 20 will soften and axiallyshrink. Because the proximal end of the cannula is bonded to the distalfiber 20, the distal end of distal fiber 20 will tend to pull away fromthe optical element 26. This will cause more light to be absorbed by thecannula, which can cause a runaway cycle of thermal deformation tooccur. This phenomenon is illustrated in FIG. 3.

FIG. 3 is a graph illustrating flux over time through a cannula 16 inwhich cannula 16 is bonded to distal fiber 20 without preconditioning.Over time the luminous flux provided by the source light graduallyincreases and the output of the probe increases correspondingly.However, at 8 minutes, the flux of the source light becomes large enoughto cause softening of the distal fiber 20, causing distal fiber 20 tobegin shrinking axially. As the distal end of distal fiber 20 moves awayfrom optical element 26, the output of the probe begins to graduallydecrease and then, at around point 11 minutes, falls off precipitously,indicating catastrophic failure of the probe.

To prevent such failure, distal optical fiber 20 can be preconditionedto release potential energy, thereby reducing or eliminating runawaythermal deformation. To precondition the distal optical fiber 20,cannula 16 is not bonded to fiber 20 after optical fiber 20 is broughtin contact with optical element 26. Instead, distal optical fiber 20 isheated to or above its softening point, but below its melting point fora defined period. This causes at least the distal portion of fiber 20 (aportion of fiber 20 starting at the distal end and ending at any pointprior to the proximal end of the cannula) to shrink axially and expandlaterally. Because distal fiber 20 is not yet bonded to cannula 16,optical element 26 and cannula 16 will move with optical fiber 20 as itshrinks axially. Consequently, potential energy can be released whilefiber 20 remains in contact with optical element 26.

FIG. 4A is a diagrammatic representation of an embodiment of a fixturefor preconditioning a fiber of an endo-illuminator in accordance withthe teachings of the present invention. In the embodiment shown in FIG.4A, proximal fiber 13 is coupled to distal fiber 20 and the cannula andoptical element assembly 32 is already assembled. Distal fiber 20 isinserted into cannula 16 until the distal end of distal fiber 20contacts the optical element 26 (shown in FIG. 2). A portion of theendo-illuminator can be clamped or otherwise secured to a work surface45. A heating member 50 can be used to heat a distal portion of thecannula 16 and optical element assembly 32. Heating member 50 can bemade of any suitable material including, but not limited to, metals andceramics, that can be heated to a desired temperature. Heating ofheating member 50 can occur by, for example, running a current throughresistors in heating member 50, preheating heating member 50 fromanother heat source or otherwise heating member 50 in a way known tothose skilled in the art. Heating member 50 can have any suitable shapeand size. According to one embodiment, heating member 50 can be a metalcylinder having an axial opening 51 with an inner diameter that isslightly larger than the outer diameter of cannula 16. The axial opening51 can extend partially or completely through the length of heatingmember 50. Heating member 50 can be coupled to a computer controlledtranslation stage 52 that allows heating member 50 to translate along atleast one axis for positioning. A computer 54 can control movement ofstage 52.

FIG. 4B is a diagrammatic representation of an embodiment of anarrangement for heating of cannula 16/optical element assembly 32. Theopening in heating member 50 can be axially aligned with cannula 16.This can be done using, for example, cameras. Heating member 50 is thenmoved over some or all of cannula 16 to a desired insertion depth.Cannula 16 remains inserted in heating member 50 for a desired dwelltime. To save time, heating member 50 is preferably heated to a desiredtemperature prior to insertion of cannula 16. However, in otherembodiments, heating member 50 may be heated after insertion of cannula16. A small force can be applied to cannula 16 as it is heated to movecannula 16 as the distal fiber 20 axially shrinks, in a direction so asto keep optical element 26 in contact with the distal end of distalfiber 20. However, the force can be limited to prevent or reduceconcavity at the distal end of distal fiber 20 as optical element 26pushes against distal fiber 20.

In another embodiment, an endo-illuminator can be preconditioned using avertical arrangement. The force of gravity on cannula 16 is a sufficientforce with which to move cannula 16. FIG. 5 is a diagrammaticrepresentation of a heating fixture with a vertical arrangement.According to one embodiment, an alignment tube 55 can be preallignedwith heating member 50. Alignment tube 55 includes an opening throughwhich cannula 16 can at least partially pass such that the distal end ofcannula 16 is aligned with the opening 51 of heating member 50. Therecan be enough clearance between alignment tube 55 and cannula 16 toallow cannula 16 to move down as the distal end of distal fiber 20softens. Heating member 50 can be coupled to a computer controlledtranslation stage 52 that allows heating member 50 to translate along atleast one axis for positioning. A computer 54 can control movement ofstage 52.

In operation, heating member 50 is heated to a desired temperature andtranslated downward (or cannula 16 translated upwards) such that thedistal end of cannula 16 is inserted in heating member 50 to a desiredinsertion depth. Heating member 50 can heat cannula 16 for a desiredtime. As the distal portion of distal fiber 20 shrinks axially, gravitywill cause optical element 26 to remain in contact with the distal endof distal fiber 20, but not cause so much force as to result inunacceptable amounts of concavity in the distal end of distal fiber 20.

The preconditioning parameters for a given heating element 50 andilluminator include the temperature of the element, insertion depth ofthe cannula 16, the dwell time (amount of time cannula 16 is inserted inheating element 50) and amount of force applied to maintain contactbetween the optical element 26 and distal fiber 20. Whether a particularset of preconditioning parameters are acceptable can be based on whetherthe endo-illuminator can experience a greater flux without catastrophicfailure after preconditioning and whether any decrease in opticalperformance due to preconditioning is acceptable. By way of example, butnot limitation, the following recipes have been found to createacceptable endo-illuminators:

For a 23 gauge wide angle illuminator probe using a heating element 50with an opening having an inner diameter of 0.100″ to 0.200″:

-   -   376 degree set point    -   0.1″ insertion depth    -   18-40 seconds dwell time    -   Insertion occurs with heating element at 400 deg F. actual        temperature with temperature on the rise.

For a 25 gauge wide angle illuminator probe using a heating element 50with an opening with an inner diameter of 0.100″ to 0.200″:

-   -   376 degree set point    -   0.1″ insertion depth    -   6-12 seconds dwell time    -   Insertion occurs with heating element is at 400 deg F. actual        temperature with temperature on the rise.

In the embodiments discussed above, the distal portion of cannula 16 andoptical element assembly 32 is heated using an external heating element50. This, in turn, causes the distal portion of distal fiber 20 to heatand soften. According to another embodiment, however, preconditioningcan be performed using high intensity light. According to thisembodiment, the endo-illuminator without the handpiece and withoutdistal fiber 20 adhered to cannula 16 can be subjected to high intensitylight, such as xenon or other light. This can cause heating andsoftening of the distal portion of distal fiber 20. If a small force,such as the force of gravity, is applied to the cannula 16 in thedirection of axial shrinkage of the fiber, cannula 16 will move with theaxially shrinking distal portion. Consequently, the optical element 26will remain in contact with the distal end of the distal optical fiber20. This can allow the residual stress in the distal portion of thedistal optical fiber 20 to be released while maintaining zero gapbetween the optical element 26 and the distal end of distal fiber 20.

Preconditioning of distal fiber 20 causes the fiber to adhere to thecannula due to lateral swelling of the fiber to fill the inner diameterof the cannula and the sticking of tacky cladding material to thecannula. This can eliminate the need to adhere the proximal portion ofcannula 16 to distal fiber 20. In other embodiments, the proximalportion of cannula 16 can be adhered to distal fiber 20 using a suitableadhesive such as Loctite 4014 by the Henkel Loctite Corporation of RockyHill, Conn.

Preconditioning of distal fiber 20 relieves the axial stress stored inthe fiber and reduces the susceptibility of the fiber to thermaldeformation from subsequent exposure to high intensity light. Data showsthat the flux can be increased greatly when compared to FIG. 3 withoutcatastrophic failure if the distal portion of distal fiber 20 has beenpreconditioned as described above. FIG. 6, for example, illustrates datafrom a 23 gauge wide angle illuminator that was preconditioned usingxenon light. Preconditioning using a heating member provides similarresults. The decreased susceptibility of the fiber to thermaldeformation is accomplished with little decrease in optical performance.FIG. 7 illustrates relative luminous intensity versus viewing angle inair of a 23 gauge wide angle illuminator without preconditioning (line60) and with preconditioning (line 65) using a heating element. FIG. 8shows a similarly modest decrease in optical performance whenpreconditioning is done using xenon light (line 70) versus the 23 gaugewide angle illuminator without preconditioning.

In the above examples, preconditioning occurs after distal optical fiber20 is coupled to proximal optical fiber 13. In other embodiments,preconditioning of distal optical fiber 20 can occur first.Additionally, similar preconditioning can be performed on devices thatutilize only one optical fiber or one gauge of optical fiber.Furthermore, while distal optical fiber 20 is discussed in terms asingle fiber, distal optical fiber 20 can be a collection of smalleroptical fibers.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,process, article, or apparatus that comprises a list of elements is notnecessarily limited only those elements but may include other elementsnot expressly listed or inherent to such process, process, article, orapparatus. Further, unless expressly stated to the contrary, “or” refersto an inclusive or and not to an exclusive or. For example, a conditionA or B is satisfied by any one of the following: A is true (or present)and B is false (or not present), A is false (or not present) and B istrue (or present), and both A and B are true (or present).

Additionally, any examples or illustrations given herein are not to beregarded in any way as restrictions on, limits to, or expressdefinitions of, any term or terms with which they are utilized. Insteadthese examples or illustrations are to be regarded as being describedwith respect to one particular embodiment and as illustrative only.Those of ordinary skill in the art will appreciate that any term orterms with which these examples or illustrations are utilized willencompass other embodiments which may or may not be given therewith orelsewhere in the specification and all such embodiments are intended tobe included within the scope of that term or terms. Language designatingsuch non-limiting examples and illustrations includes, but is notlimited to: “for example”, “for instance”, “e.g.”, “in one embodiment”.

What is claimed is:
 1. A illuminator method comprising: inserting anoptical fiber through a proximal portion of a cannula/optical elementassembly until the distal end of the optical fiber contacts the opticalelement; heating a distal portion of the optical fiber to between asoftening temperature and a melting temperature for a period of time tocause the distal portion to axially shrink; and moving the opticalelement so that the optical element is in contact with the distal end ofthe optical fiber when the distal portion of the optical fiber hasaxially shrunk.
 2. The method of claim 1, wherein moving the opticalelement so that the optical element is in contact with the distal end ofthe optical fiber when the distal portion of the optical fiber hasaxially shrunk further comprises applying a force to the cannula/opticalelement assembly to maintain the optical element in continuous contactwith the distal end of the optical fiber while the optical fiber axiallyshrinks.
 3. The method of claim 1, wherein heating the distal portioncomprises applying a high intensity light to the optical fiber to raisethe temperature of the distal portion to between the softening point andmelting point of the optical fiber.
 4. The method of claim 1, whereinheating the distal portion comprises applying heat with a heatingmember.
 5. The method of claim 4, wherein the heating member defines anopening into which the cannula and optical element assembly can beinserted.
 6. The method of claim 5, further comprising heating theheating member to at least a minimum temperature and inserting thecannula/optical element assembly into the opening to an insertion depth.7. The method of claim 6, wherein the minimum temperature is at least350 degrees.
 8. The method of claim 6, wherein the minimum temperatureis at least 400 degrees.
 9. The method of claim 6, wherein the period oftime is in a range of 6 to 40 seconds.
 10. The method of claim 9,wherein the cannula/optical element assembly is inserted to an insertiondepth of between 0.05 inches and 0.2 inches.
 11. The method of claim 6,further comprising vertically aligning the cannula/optical elementassembly with the opening using an alignment tube.
 12. The method ofclaim 11, wherein moving the optical element so that the optical elementis in contact with the distal end of the optical fiber when the distalportion of the optical fiber has axially shrunk further comprisingallowing gravity to move the cannula/optical element assembly.
 13. Themethod of claim 1 further comprising bonding a proximate portion of thecannula to the optical fiber after moving the optical element.
 14. Anilluminator method comprising: inserting an optical fiber through aproximal portion of a cannula until the distal end of the optical fibercontacts a lens; vertically aligning the cannula with an opening definedby a heating member; lowering the heating member until the cannula isinserted a desired insertion depth in the opening; heating a distalportion of the optical fiber to between a softening temperature and amelting temperature for a period of time to cause the distal portion toaxially shrink; and allowing the cannula to move so that the lensremains in contact with the distal end of the optical as the distalportion axially shrinks.
 15. The method of claim 14, wherein the cannulais one of a 23 gauge or 25 gauge cannula.
 16. The method of claim 15,wherein the lens is a sapphire lens for a wide angle illuminator. 17.The method of claim 14, further comprising heating the heating member toat least 350 degrees F.
 18. The method of claim 14, further comprisingheating the heating member to at least 400 degrees F.
 19. The method ofclaim 14, wherein the period of time is in a range of 6 to 40 seconds.20. The method of claim 14, wherein the cannula and optical elementassembly is inserted to an insertion depth of between 0.05 inches and0.2 inches.
 21. The method of claim 14, further comprising using analignment tube to vertically align the cannula with the opening.